The following description of prior-art technique, problems of known systems as well as the object and features of the invention will therefore as non-limiting examples be aimed mainly at this field of application. However, it should be emphasized that the invention can be used in optional floorboards which are intended to be joined in different patterns by means of a mechanical joint system. The invention may thus also be applicable to homogeneous wooden floors, laminate floors with a surface of laminate and a core of e.g. fiberboard and floors with a surface of plastic and/or cork and the like.
Traditional parquet floors are usually laid in a floating manner, i.e. without glue, on an existing subfloor which does not have to be quite smooth or plane. Any irregularities are eliminated by means of underlay material in the form of e.g. cardboard, cork or foam plastic which is laid between the floorboards and the subfloor. Floating floors of this kind are usually joined by means of glued tongue-and-groove joints, (i.e. joints with a tongue on one floorboard and a tongue groove on an adjoining floorboard) on long side and short side. In laying, the boards are joined horizontally, a projecting tongue along the joint edge of one board being inserted into a tongue groove along the joint edge of an adjoining board. The same method is used on long side as well as short side, and the boards are usually laid in parallel both long side against long side and short side against short side.
In addition to such traditional floors which are joined by means of glued tongue/tongue groove joints, floorboards have been developed in recent years, which do not require the use of glue but which are instead joined mechanically by means of so-called mechanical joint systems. These systems comprise locking means which lock the boards horizontally and vertically. The mechanical joint systems can be formed by machining the core of the board. Alternatively, parts of the locking system can be made of a separate material which is integrated with the floorboard, i.e. already joined with a floorboard in connection with the manufacture thereof at the factory. The floorboards are joined, i.e. interconnected or locked together, by various combinations of angling, snapping-in and insertion along the joint edge in the locked position. By interconnection is here meant that floorboards with connecting means are mechanically interconnected in one direction, for instance horizontally or vertically. By locking-together, however, is meant that the floorboards are locked both in the horizontal and in the vertical direction.
The principal advantages of floating floors with mechanical joint systems are that they can be laid quickly and easily by different combinations of inward angling and snapping-in. They can also easily be taken up again and be reused in some other place.
All currently existing mechanical joint systems and also floors intended to be joined by gluing have vertical locking means which lock the floorboards across the surface plane of the boards. The vertical locking means consist of a tongue which enters a groove in an adjoining floorboard. The boards thus cannot be joined groove against groove or tongue against tongue. Also the horizontal locking system as a rule consists of a locking element on one side which cooperates with a locking groove on the other side. Thus the boards cannot be joined locking element against locking element or locking groove against locking groove. This means that the laying is in practice restricted to parallel rows. Using this technique, it is thus not possible to lay traditional parquet patterns where the boards are joined long side against short side in (herringbone pattern) or in different forms of diamond patterns.
Such advanced patterns have originally been laid by a large number of wood blocks of a suitable size and shape being glued to a subfloor, according to a desired pattern, possibly followed by grinding to obtain an even floor surface and finishing in the form of e.g. varnish or oil. The wood blocks according to this technique have no locking means whatever, since they are fixed by gluing to the subfloor.
Another known method of laying advanced patterns implies that the wood blocks are formed with a groove along all edges of the block. When the wood blocks are then laid, tongues are inserted into the grooves in the positions required. This results in a floor where the wood blocks are locked in the vertical direction relative to each other by the tongue engaging in tongue grooves of two adjoining wood blocks. Optionally this method is supplemented with gluing to lock the floor in the horizontal directions and to lock the floor in the vertical direction relative to the subfloor.
U.S. Pat. No. 1,787,027 (Wasleff) discloses another system for laying a herringbone parquet floor. The system comprises a plurality of wood blocks which are laid on a subfloor to form a herringbone parquet floor. Each wood block is provided with a set of tongues and tongue grooves which extend over parts of each edge of the wood block. When the wood blocks are laid in a herringbone pattern, tongues and tongue grooves will cooperate with each other so that the wood blocks are locked together mechanically in both the vertical and the horizontal direction. The tongues and tongue grooves that are shown in Wasleff, however, are of a classical type, i.e. they cannot be snapped or angled together, and the locking effect is achieved only when a plurality of wood blocks are laid together to form a floor. The system according to Wasleff consists of two types of wood blocks, which are mirror inverted relative to each other as regards the location of tongues and tongue grooves. The design of the locking system is such that a shank-end mill is necessary to form the tongue grooves shown. This is a drawback since machining using a shank-end mill is a relatively slow manufacturing operation.
U.S. Pat. No. 4,426,820 (Terbrack) discloses that floorboards can be joined long side against short side if the floor consists of two different floorboards which a joint system which can be laid merely by inward angling, which is not displaceable in the locked position and in which floorboards cannot be joined by snapping-in. Moreover FIGS. 11 and 23 show floorboards which are mirror inverted relative to each other. This is, however, not discussed in detail in the description. Col. 5, lines 10-13, seems to contain an indication that it is possible to join short side and long side. However, it is not shown how a complete floor can be joined using such floorboards to form a pattern. Owing to the non-existence of displaceability in the joined position and snappability, it is not possible to create, using such floorboards as disclosed by Terbrack, a floor of the type at which the present invention aims.
U.S. Pat. No. 5,295,341 (Kajiwara) discloses snappable floorboards which have two different long sides. One part of the long side is formed with a groove part and another part with a tongue part. Nor are such floorboards displaceable in the locked position. The manufacture is complicated, and nor can they be used to provide the desired pattern.
Boden Wand Decke (Domotex, January 1997) shows a laminate floor where floorboards with different surfaces have been joined to form a floor having a simple pattern. It is also shown that floorboards have been joined long side against short side, but only in such a manner that all the short sides which are joined with a long side extend along a straight line. Consequently, this is an application of a prior-art system.